Beta sheet: Difference between revisions
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===Beta sheets in amyloid fibrils=== | ===Beta sheets in amyloid fibrils=== | ||
==History== | ==History== | ||
Alpha helices and beta sheets are named after two conformations of keratin, a fiber occuring in mammals (wool, hair, quills) <ref>PMID: 15240497</ref>. Alpha keratin is composed of [[coiled coil| | Alpha helices and beta sheets are named after two conformations of keratin, a fiber occuring in mammals (wool, hair, quills) <ref>PMID: 15240497</ref>. Alpha keratin is composed of [[coiled coil|coiled coils]] of alpha helices, whereas hard stretching these fibers in water changes the conformation to beta sheets. The two conformations show different diffraction data under X-ray illumination. | ||
==Experimental evidence== | ==Experimental evidence== | ||
Apart from the historical fiber diffraction data, various spectroscopic techniques may be used to show the presence of beta sheets. Circular dichroism (CD) or infrared (IR) spectroscopy allows an estimate of the beta sheet content of a protein sample. NMR spectroscopy, after resonance assignment, allows secondary structure assignment residue by residue based on chemical shifts of the alpha carbon and beta carbon resonances. | Apart from the historical fiber diffraction data, various spectroscopic techniques may be used to show the presence of beta sheets. Circular dichroism (CD) or infrared (IR) spectroscopy allows an estimate of the beta sheet content of a protein sample. NMR spectroscopy, after resonance assignment, allows secondary structure assignment residue by residue based on chemical shifts of the alpha carbon and beta carbon resonances. | ||
